Alfalfa producers can better interpret results from laboratory analysis of their alfalfa if they understand how those results are obtained. Forage quality test reports from the OSU Soil, Water, & Forage Analytical Laboratory list 24 quality traits for each sample submitted for routine forage analysis. In actuality only four traits are measured, while 20 are derived (i.e., calculated from an equation using the measured traits). 

The relationship between the measured and derived traits are depicted in the diagram. As can be seen, the four measured properties are Total Nitrogen, ADF (acid detergent fiber), NDF (neutral detergent fiber), and Moisture. These four traits can be measured directly using traditional chemical analysis or can be measured indirectly using near infrared reflectance spectroscopy (NIRS). Either way the derived traits are calculated from the same equations. 

Some alfalfa producers and buyers like to know what mathematical equations are used to calculate the derived values since several equations have been developed through time and differences frequently exist from region to region and laboratory to laboratory. Following are the methods and equations used by the OSU laboratory to measure or derive the traits listed on our forage test reports: